In a medium-size bowl, sift together the flour, baking powder, baking soda, and salt.

In a large bowl, add the vegetable oil. Add the sugar a little bit at a time, and continue beating until the mixture is fluffy.

Add the eggs to the mixture in the large bowl and beat well.

Add some of the flour mixture to the large bowl and beat well. Then add some of the mashed bananas and beat some more. Continue adding flour, then bananas, then flour, then bananas, until everything is mixed in.